1. Field of the Invention
The present invention relates to a fiber optic light source, and more particularly to a high-power and wide-band fiber optic light source adapted to use amplified spontaneous emission (ASE) light as a secondary pumping source.
2. Description of the Related Art
A continued research is being conducted for wide-band light sources, and as a result, they have a variety of applications to be used as gyrosensors, light sources for testing the optical elements, and light sources of sliced spectrums to provide inexpensive access networks.
In particular, the light sources which use ASE light emitted from a fiber doped with a rare-earth elements such as erbium are well known as being an excellent wide-band light source in that they exhibit wide spectrum, high power, and low loss characteristics. All research efforts, which have been made for such erbium-doped fiber (EDF) wide-band light sources, are associated with a wavelength band of 1,520 to 1,560 nm in the range that most optical communication elements and conventional EDF amplifiers operate.
However, a recent demand for the expansion of optical communication resulted in more active developments of optical amplifiers operating in long-wavelength bands. In this regard, it has also been necessary to develop light sources having high efficiency, high-power and wide-band spectrums operating in long-wavelength bands.
FIG. 1 is a schematic view illustrating a conventional EDF light source. Referring to FIG. 1, a light beam, which are generated while passing through the EDF regions, EDF I and EDF II, and is pumped by a forward pumping light means, and then emitted as an output light 20.
The forward pumping light means comprises a laser diode 10 having an operating wavelength of 980 nm. The laser diode 10 is coupled to the EDF light source by means of a wavelength division multiplexing (WDM) coupler 30. In the illustrated case, an optical isolator 40 is also arranged at the output terminal of the EDF light source in order to guide the travel direction of the light in one direction. However, the EDF light source depicted in FIG. 1 produces undesirable low intensity of output light and narrow operating wavelength band.
FIG. 2 is a graph depicting ASE output spectrums of conventional EDF light sources which have the above mentioned configuration while operating the optical fibers for EDF II at different lengths, accordingly. Referring to FIG. 2, it can be found that the intensity and emission bandwidth of the ASE light outputted in the above mentioned configuration decrease depending on the length of the second erbium-doped fiber (EDF) region, namely, EDF II.